Four-wheel drive vehicles which are operable in either a two-wheel drive mode or a four-wheel drive mode have gained widespread popularity. Axle disconnect mechanisms, or differential disconnect mechanisms or assemblies for such vehicles are known.
Commonly used disconnect mechanisms for four-wheel drive vehicles disconnect only one of the two output shafts on an axle assembly which is driven part time. This causes the pinion gears and the side gears of the differential to rotate due to back driving, although the differential case remains stationary. This is not compatible with speed-sensitive limited slip differentials. Also, single axle disconnect mechanisms may cause noise and wear and poor fuel economy due to rotation of the differential components while the vehicle is in two-wheel drive mode.
Various dual disconnect differential assemblies or mechanisms have been proposed. These mechanisms in general have a number of moving parts, are fairly complex, and would be suitable only for installation on relatively wide vehicles because of the space required. None has achieved commercial acceptance.